IPAC Visiting Graduate Research Fellows

This will be the final presentations by this years IPAC Visiting Graduate Research Fellows describing their progress. Details of speakers and abstracts are below: Speaker: G. Privon Abstract: Dynamical models of galaxy mergers can enable a detailed comparison of predictions from simulations and observations. This can shed light on processes thought to be important in galaxy evolution, including star formation and active galactic nuclei. I will demonstrate a dynamically motivated merger stage classification based on newly obtained dynamical models. I will also show progress comparing simulated star formation from matched hydrodynamical simulations with observational tracers of star formation. Speaker: E. Hardegree-Ullman Abstract: Astronomers have long attributed the observation of infrared emission features (at ~3.3, 6.2, 7.7, 8.6, and 11.3 microns) from the gas phase interstellar medium to the  presence of polycyclic aromatic hydrocarbons (PAHs). These PAHs are thought to account for a significant portion of the carbon reservoir in the Milky Way and as such could be of great astrobiological importance. While PAH emission has not been detected toward embedded young stellar objects (YSOs), tentative detections of absorption features at ~3.3 and 11.3 microns have been reported (Sellgren et al. 1994, 1995; Bregman et al. 2000) indicating that the PAHs in these systems are frozen onto the icy mantles of dust grains. My work reexamines YSO spectra (Boogert et al. 2008) to constrain PAH column densities in YSO systems, as well as to estimate the contribution of frozen PAHs to unidentified absorption features. To do so, I used laboratory experiments to determine the band positions, widths, and strengths of pyrene frozen in H2O and D2O ices. Speaker: H. Meng Abstract: Most models of protoplanetary disks assume an inner wall of disk extension where dust particles are depleted by vaporization or gravitational clearance. Theories and spectroscopic evidence suggest that such disk walls should be very close to their central young stellar objects (YSOs) and have defies the resolution of current imaging technology. Here we report the first detection of an inner disk wall around a Class I YSO, YLW 16B, in ~1 Myr-old star forming region rho Ophiuchi, by measuring the time lag between the near-infrared variations of stellar radiation and the 4.5 um response from the disk. The observed time lag corresponds to a distance of >0.13 AU for light travel. This is the only YSO with high signal-to-noise ratio and correlated short-term variations in our field of 27 sources, though more YSOs are found to be variable on hourly timescales.